The present invention relates to an apparatus and a method for performing cylinder judgment of an engine based on the output number of cylinder judgment signals between reference crank angle positions.
Conventionally, there has been a cylinder judgment apparatus for performing cylinder judgment based on the output number of cylinder judgment signals between reference crank angle positions as disclosed in Japanese Unexamined Patent Publication No. 5-106500 or No. 10-030488.
In Japanese Unexamined Patent Publication No. 5-106500, the constitution is such that the cylinder judgment signals of the number corresponding to the number of cylinders between reference crank angle positions are output.
The apparatus disclosed in Japanese Unexamined Patent Publication No. 10-030488 has two cam sensors. The cylinder judgment is carried out based on the number of signals output between the reference crank angle positions from one of the two cam sensors. When the cylinder judgment cannot be carried out based on the number of signals from the one cam sensor, the cylinder judgment is carried out based on the number of signals from the other cam sensor.
As disclosed in Japanese Unexamined Patent Publication No. 5-106500, however, if the cylinder judgment signals of the number corresponding to the number of cylinders is output, for instance, in a six cylinder engine, a cylinder plate for outputting the cylinder judgment signals requires six portions to be detected at a maximum between the reference crank angle positions. Therefore, in such a constitution that a magnetic sensor is used to detect projections formed on a signal plate, the signal plate cannot be miniaturized.
In the apparatus disclosed in Japanese Unexamined Patent Publication No. 10-303488, it is required that a specific cylinder can be identified based only on a signal from the one cam sensor. Therefore, there is a small degree of freely setting the number of cylinder judgment signals.
In view of the foregoing problems, the present invention has been achieved and has an object of providing an apparatus and a method for judging cylinders wherein cylinder judgment can be carried out with a small number of portions to be detected which are to be formed on a signal plate of a cam sensor, and a high degree of freely setting the number of cylinder judgment signals can be obtained.
For achieving the above object, the present invention is constituted so that a plurality of cam sensors are provided, and the output number of cylinder judgment signals between reference crank angle positions are counted up for each of the plurality of cam sensors to carry out cylinder judgment based on combinations of the output number of the counted cylinder judgment signals.
According to the above constitution, where there are a first cam sensor and a second cam senor as the cam sensor, if each of the cam sensors outputs the cylinder judgment signal of 0 or 1 between the reference crank angle positions, four pattern combinations of 2xc3x972 can be produced, thereby capable of distinguishing the cylinders into 4.
Accordingly, it is not required for one cam sensor to output the cylinder judgment signal in the same kind of pattern as the number of cylinders so that the number of portions to be detected formed on the signal plate can be reduced to make the diameter of the signal plate small. Further, the number of cylinder judgment signals to be output from a single cam sensor is not required to correspond to a specific cylinder. Thus, a high degree of freely setting the number of cylinder judgment signals can be achieved.
Here, a cam sensor may be disposed on each of an intake side camshaft and an exhaust side camshaft of an engine. Further, a cam sensor may be disposed on each bank of a V-type engine.
Also, in a case that a valve timing is changed with a change in a rotation phase of a camshaft relative to a crankshaft, the constitution may be such that the cam sensor disposed on the camshaft, whose rotation phase is controlled, outputs at least one cylinder judgment signal between the reference crank angle positions, to thereby detect the rotation phase based on a phase difference between the cylinder judgment signal from the cam sensor disposed on the camshaft, whose rotation phase is controlled, and the reference crank angle position.
Further, a crank angle sensor may be disposed for outputting a unit angle signal for each unit crank angle, the sensor being constituted not to output the unit angle signal for each stroke phase difference between cylinders. The position where the crank angle sensor did not output the unit angle signal is judged based on the period of the unit angle signals to be detected as the reference crank angle position.
The other objects and features of the present invention will be understood from the following description of the embodiments with reference to the accompanying drawings.